The present invention relates to an improvement in a sludge withdrawal mechanism of the type disclosed in U.S. Pat. No. 3,800,955 assigned to the assignee of the present invention. The subject matter of that patent which is not inconsistent with the present disclosure is incorporated herein by reference.
The sludge withdrawal or removal mechanism disclosed in the above mentioned patent consists of a pair of rake arms that are rotated within a tank and the rake arms have V-shaped plows defined thereon so that the settled sludge is concentrated in localized areas on the tank bottom. A pair of conduits lead from each of the localized areas to a collection zone. By utilizing two different conduits of the same or different sizes, a first flow range can be developed utilizing only the first conduits, a second flow range can be developed by utilizing only the second conduits and a third flow range can be developed by utilizing both conduits.